The present invention is generally directed to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner particles. In embodiments, the present invention is directed to an in situ chemical toner preparation without the utilization of the known pulverization and/or classification methods, and wherein in embodiment toner particles with an average volume diameter of from about 1 to about 25, and preferably from 1 to about 10 microns and narrow GSD of, for example, from about 1.16 to about 1.26 as measured on the Coulter Counter can be obtained, and wherein the reactor agitator is equipped with an impeller to mix the pigment dispersion and the latex, wherein the mixing results in a low shear thereby avoiding the disadvantages of high shear devices such as a homogenizer. These disadvantages include the malfunctioning of the equipment, such as seal leaks, resulting in loss of materials and shearing efficiency, loss of materials in the recirculating lines, resulting in lower toner yields, additional piping and equipment costs, and extra maintenance costs. The resulting toners produced with the use of high shear devices, and more specifically, at high shear speeds, for example a rotor stator operating a 3,000 to 18,000 RPM, have a major disadvantage and that is the process time is extended for a period of time of up to about 29 percent, compared to the process time wherein these is selected a low shear device. The resulting toners produced in accordance with the present invention can be selected for known electrophotographic imaging, printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process comprised of dispersing a latex or emulsion mixture comprised of suspended submicron resin particles of from, for example, about 0.01 micron to about 1 micron or less in volume average diameter in an aqueous solution containing an ionic surfactant in amounts of from about 1 percent to about 10 weight percent and nonionic surfactant in amount of from about 0 percent to about 5 weight percent, and shearing this mixture at low, or slow speeds of from about 100 to about 900 and preferably from about 150 to about 600 revolutions per minute (rpm) with a pigment dispersion and optionally toner additives like a charge control agent, and which dispersion contains a counterionic surfactant with opposite charge to the ionic surfactant of the latex in an amount of from about 0.5 percent (weight percent throughout unless otherwise indicated) to about 10 percent, thereby causing a flocculation of resin particles, pigment, and optional charge control agent, followed by heating at about 5 to about 40.degree. C. below the resin Tg and preferably about 5 to about 25.degree. C. below the resin Tg while stirring of the flocculent mixture which is believed to form statically bound toner aggregates of from about 1 micron to about 10 microns in volume average diameter comprised of resin, pigment and optionally charge control particles; adding further surfactant in order to stabilize the aggregates, and thereafter, heating the formed bound aggregates about above the Tg (glass transition temperature) of the resin. The size of the aforementioned statistically bonded aggregated particles in embodiments can be controlled by adjusting the temperature in the below the resin Tg heating stage. An increase in the temperature causes an increase in the size of the aggregated particle. This process of aggregating submicron latex and pigment particles is kinetically controlled, that is the temperature increases the process of aggregation. The temperature also controls in embodiments the particle size distribution of the aggregates, for example the higher the temperature the narrower the particle size distribution, and this narrower distribution can be achieved in, for example, from about 0.5 to about 24 hours and preferably in about 1 to about 3 hours time. The addition of more, or extra stabilizer followed by heating the mixture above or in embodiments equal to the resin Tg generates toner particles with, for example, an average particle volume diameter of from about 1 to about 25, preferably 10 microns, containing pigment and polymer.
The present invention in embodiments relates to the preparation of toners comprised of thermoplastic resin and pigment, and wherein the preparation comprises an emulsion/aggregation/coalescence method as indicated herein, wherein low shear is selected, and wherein a latex of resin containing an anionic surfactant and a nonionic surfactant is mixed with a water dispersion of pigment and a cationic surfactant to form a homogeneous gel at a viscosity of from about 300 centipoise to about 1,200 centipoise. High viscosity, for example 1,000 to 1,200 centipoise, usually requires the use of a high shear stator rotator device, such as a polytron at high speeds (3,000 to 18,000 rpm) for blending for a period of 5 to 30 minutes, during which time the mixture is continuously being recycled to achieve a homogeneous blend of pigment and latex particles. These homogeneous blends can now also be obtained by the invention process using a reactor agitator equipped with turbine blades and stirring at speeds of from about 100 to 900 rpm, and preferably at low speeds of from about 150 to about 600 rpm, for an effective period of time such as, for example, from about 10 minutes to about 150 minutes. Toner compositions, or toner particles of excellent volume average diameter, superior GSD, for example of 1.20, and the like are obtainable with the processes of the present invention.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Also, see column 9, lines 50 to 55, wherein a polar monomer, such as acrylic acid, in the emulsion resin is necessary, and toner preparation is not obtained without the use, for example, of acrylic acid polar group, see Comparative Example I. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70, are obtained. This process is thus directed to the use of coagulants, such as inorganic magnesium sulfate, which results in the formation of particles with a wide GSD.
Emulsion/aggregation processes for the preparation of toners are illustrated in a number of patents, the disclosures of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,346,797, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797.